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PolarConverter
What it is
PolarConverter is a free, open-source Java command-line utility for changing Minecraft Java Edition worlds from Anvil format into Polar files for Minestom-based servers. It can process an entire world, or limit work to chunks inside an optional radius measured from coordinates (0,0). The source folder must include a region directory and level.dat, and Java 25 or newer is required. Before conversion, the tool compares the world’s DataVersion with the version supported by Minestom; a mismatch ends the process with an error. PolarConverter starts a minimal offline Minestom server to supply block registries and NBT support, reads Anvil chunks, converts block and metadata information, and writes a .polar file. Its listed dependencies are Minestom and Polar, which provides Polar world-format support. The project uses the MIT License and is available on GitHub, although its releases page reports no releases.
For and against
For
- Converts complete worlds or radius-limited chunks
- Outputs Polar-format .polar files
- Uses a minimal offline Minestom server
- MIT-licensed open-source project
- Free command-line tool
Against
- Requires Java 25 or later
- DataVersion mismatch stops conversion
- Input must contain region and level.dat
- GitHub lists no releases
The verdict
PolarConverter focuses on a specific Anvil-to-Polar workflow for Minestom servers. Check the required Java version and DataVersion compatibility before starting.
Who it suits
It suits Minecraft Java Edition users preparing Anvil worlds for Minestom-based servers, especially those needing full-world or radius-limited conversion.
On the record
- Conversion process
- It starts a minimal offline Minestom server for block registries and NBT support, reads Anvil chunks, converts blocks and metadata, and writes a .polar file.github.com · read 4 Oct 2026
- Conversion scope
- It supports full world conversion or conversion within a specified chunk radius around (0,0).github.com · read 7 Oct 2026
- Dependencies
- The project lists Minestom and Polar as dependencies for server library and world format support.github.com · read 7 Oct 2026
- Downloads
- The GitHub releases page states that there are no releases.github.com · read 7 Oct 2026
- Full-world conversion
- The converter can process an entire world.github.com · read 4 Oct 2026
- Input files
- The input world folder must contain a region folder and level.dat file.github.com · read 7 Oct 2026
- Input requirements
- The project requires Java 25+ and a Java Edition Anvil world containing a region folder and level.dat file.github.com · read 4 Oct 2026
- Intended users
- The project describes compatibility with Minestom based servers, making it relevant to users converting Minecraft worlds for those servers.github.com · read 7 Oct 2026
- License
- The project states that it is licensed under the MIT License.github.com · read 7 Oct 2026
- Maker profile
- The GitHub profile describes its developer as focused on creating software, usually for Minecraft.github.com · read 4 Oct 2026
- Notable limit
- Conversion stops with an error when the world's DataVersion does not match the version supported by Minestom.github.com · read 7 Oct 2026
- Operation
- The tool starts a minimal offline Minestom server to provide block registries and NBT support during conversion.github.com · read 7 Oct 2026
- Output
- The converter writes the result as a .polar file.github.com · read 7 Oct 2026
- Partial conversion
- An optional radius limits conversion to chunks within that radius of coordinates (0,0).github.com · read 4 Oct 2026
- Purpose
- PolarConverter converts Minecraft Java Edition worlds in Anvil format into Polar world format for Minestom based servers.github.com · read 7 Oct 2026
- Requirements
- The README lists Java 25 or later and a Minecraft Java Edition world in Anvil format as requirements.github.com · read 7 Oct 2026
- Version check
- Before converting, it checks that the world's DataVersion matches the Minestom server's supported version.github.com · read 7 Oct 2026
- Version requirement
- The world’s DataVersion must match the Minestom server’s supported version; otherwise conversion stops with an error.github.com · read 4 Oct 2026
